Tuesday, 7 June 2016

This week Tim Kearsey
and TW:eed Team colleagues Carys Bennett, David Millward, Sarah Davies, Mel
Leng and John Marshall have had a paper published in the journal Palaeogeography,
Palaeoclimatology, Palaeoecology. You can see a copy of the paper online here.
For this part of the project the team studied fossilised soils (palaeosols)
from the outcrops that the tetrapods were found in, from two field sites and in
the borehole. By studying palaeosols we can try to find out what the
environment and climate was like out of the water. Was there anything special
about the landscape that caused the tetrapods to evolve to become terrestrially
adapted?

One of the figures from Tim’s paper that
documents the different types of roots and rooting depths present

We discovered
that the landscape was covered with lots of different habitats, including marsh
wetlands, small stands of trees and areas of low vegetation. The overall
landscape would have looked similar to the Florida Everglades of the USA.
Fossilised root traces suggest that there was a wide range of different types
of vegetation from trees to small ferns.

Tim pointing out a large tree root that
was in situ at one of the field sites

From the
geochemistry of the palaeosols we found that the area mean annual rainfall was
1000 –1500 mm per year in the Carboniferous. However, this rainfall was
strongly seasonal as there is evidence of deep cracks in the soils which
suggest a pronounced dry season. This confirms what others have found that at
the time the tetrapods were living, that Southern Scotland was in a monsoonal
tropical climate. When it rained large areas got flooded and may have presented
new habitats for the tetrapods. However, many of these would have dried out in
the dry season meaning the ability to live both on land and in the water would
be an advantage.